Support Areas and Volumes for Humanoid Locomotion under Frictional Contacts

Abstract

Humanoid locomotion on horizontal floors was solved by closing the feedback
loop on the Zero-tiling Moment Point (ZMP), a measurable dynamic point that
needs to stay inside the foot contact area to prevent the robot from falling
(contact stability criterion). However, this criterion does not apply to
general multi-contact settings, the "new frontier" in humanoid locomotion.

In this talk, we will see how the ideas of ZMP and support area can be
generalized and applied to multi-contact locomotion. First, we will show how
support areas can be calculated in any virtual plane, allowing one to apply
classical schemes even when contacts are not coplanar. Yet, these schemes
constraint the center-of-mass (COM) to planar motions. We overcome this
limitation by extending the calculation of the contact-stability criterion from
a support area to a support cone of 3D COM accelerations. We use this new
criterion to implement a multi-contact walking pattern generator based on
predictive control of COM accelerations, which we will demonstrate in real-time
simulations during the presentation.